The invention relates to a printing unit of a printing press.
Printing units of web-fed rotary presses, in particular of newspaper presses, have a plurality of press units, every press unit comprising a transfer cylinder, a form cylinder and an inking unit and damping unit. Furthermore, printing units of this type can have impression cylinders, it being possible for an impression cylinder to interact with one or more transfer cylinders of different press units. In addition to printing units which have impression cylinders of this type, printing units which do not have any impression cylinders are also known, the transfer cylinders of two press units rolling on one another in printing units of this type without impression cylinders. Rubber blankets are usually clamped on the transfer cylinders and printing plates on the form cylinders, for which reason the transfer cylinders are also called rubber-covered cylinders and the form cylinders are also called plate cylinders. The inking unit of a press unit serves to apply printing ink onto the form cylinder of the press unit, whereas the damping unit serves to apply a damping solution onto the form cylinder of the press unit.
In web-fed rotary presses, a distinction is made in principle between printing units which apply the damping solution onto the form cylinder of the respective press unit via direct damping-solution supply or via indirect damping-solution supply. In press units having indirect damping-solution supply, a damping-solution applicator roll of the damping unit rolls firstly on the form cylinder and secondly on an ink distributor roll of the inking unit of the respective press unit, the damping solution being applied to the form cylinder firstly directly via the damping-solution applicator roll and secondly indirectly via ink applicator rolls of the inking unit. In press units of this type having indirect damping-solution supply, the damping-solution applicator roll is driven by way of friction by the ink distributor roll. In contrast, in press units having direct damping-solution supply, the damping-solution applicator roll rolls only on the form cylinder and not on the ink distributor roll, with the result that the damping solution passes to the form cylinder only directly via the damping-solution applicator roll. In press units having direct damping-solution supply, the damping-solution applicator roll is either assigned a dedicated drive or the damping-solution applicator roll is driven mechanically via a gear mechanism. Printing units or press units of printing units of this type have not been disclosed up to now which also make direct damping-solution supply possible in the event of a machine-side design for indirect damping-solution supply and accordingly in the event of a damping-solution applicator roll without a dedicated drive or without an associated gear mechanism.
Proceeding from this, the present invention is based on the problem of providing a novel printing unit of a printing press.
By way of the printing unit according to the invention, the damping solution can, furthermore, be applied via direct damping-solution supply, in addition to indirect damping-solution supply, in such a way that the damping-solution applicator roll which is set away from the ink distributor roll and is driven by way of friction by the form cylinder rolls only on the form cylinder and thus applies the damping solution to the form cylinder only directly via the damping-solution applicator roll, it being possible, in the event of indirect damping-solution supply, which is selected by the controller or the machine and in the print set-up mode in which the damping-solution applicator roll rolls exclusively on the ink distributor roll and is driven by way of friction by the ink distributor roll, to set the damping-solution applicator roll away from the ink distributor roll of the inking unit more quickly in order to switch over to direct damping-solution supply than it is possible to set the damping unit and thus the damping-solution applicator roll against the form cylinder.
Accordingly, firstly indirect damping-solution supply and secondly direct damping-solution supply in the event of a damping-solution applicator roll which is driven only by way of friction are possible using the printing unit according to the invention, without there being a risk of damaging the damping-solution applicator roll during the switchover from indirect damping-solution supply to direct damping-solution supply. A dedicated drive for the damping-solution applicator roll or a gear mechanism which is assigned to the damping-solution applicator roll can be dispensed with.